April 19, 2014

Homework Help: Chem >Jai

Posted by Connie on Saturday, September 10, 2011 at 4:49pm.

Posted by Connie on Saturday, September 10, 2011 at 10:36am.

What is the amount of energy of calories to heat 8.5g of water from 15 C to 36 C?

I think you take 8.5g x 21 degree C, but then I am stuck. Thank you

Chem - Jai, Saturday, September 10, 2011 at 10:50am

amount of energy absorbed or released is given by
Q = mc*(T2 - T1)
Q = heat (in Joules)
m = mass (in grams)
c = specific heat capacity (J/g-K)
T = temperature (in Celsius or Kelvin)
*note that Q is (+) if the object absorbed heat, and (-) if it released heat.
for water, c = 4.184 J/g-K (you can find this in books or you can google this)
Q = 8.5*4.184*(36-15)
Q = ?
now solve for Q. units in Joules.

hope this helps~ :)
First, thank you, I get 746.844J but my book says the answer is 180 cal---what am I not doing correctly?

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